on the boat w/500 psi

[mongodives]

I "learned" the 500psi rule from Boat dive ops in Hawaii. When I asked the DM later about it, I was told that if a tank is empty the place they get them filled required it to be inspected, and inspections cost money.

Had nothing to do with actual gas management, just dollars.

 

[SoccerJeni]

This survey is based upon what I have read in this thread: http://www.scubaboard.com/forums/ne...9-seeking-input-low-air-no-air-situation.html

When I learned to dive I was always taught to be back on the boat with 500 psi or back at the surface with 500 psi. Unfortunately while I was told what to do, I was not trained in how to do it. I learned about SAC, turn pressure, etc., here on SB. Where did you learn how to end up "back at the boat with 500 psi"?

Multiple votes are allowed as one person may have had the opportunity to learn these concepts in different places.

I'm wondering if people are confused? Or if it is just me (very possible). It seems like there are a lot of responses about knowing the rule. However, Crush, you were asking if they were taught HOW TO execute the dive so they followed the rule, right?

I guess I'm suprised at how many people have said they learned how to plan out their gas from OW. I was told the rule of thirds, but I don't think that's really a good plan, because different dives require different plans...such as the post that sparked this question. I'm just confused if everyone learned a planning method or just guidelines to go by?

 

[syntaxerrorsix]

Is there an echo in here?

I believe I stated that working PSI isn't relevant without knowing the working volume.

Having 500 PSI on the boat has no bearing on me in twin 80's as I'll have twice the gas as a diver with a single.


So to recap the recap. 500PSI means NOTHING unless every single diver on the boat is using the same cylinders and it's been agreed what the basic minimum volume of remaining gas is acceptable.

ETA

Out of 5 spg's I've been using over the last 7 years I have exactly none of them that read differently. Maybe it's luck. As long as they all read zero I know what to expect.

 

[GrumpyOldGuy]

Did any of your gauges indicate more air than actual or were they all biased like mine to read less than actual?

 

[SoccerJeni]

Is there an echo in here?

I believe I stated that working PSI isn't relevant without knowing the working volume.

Having 500 PSI on the boat has no bearing on me in twin 80's as I'll have twice the gas as a diver with a single.


So to recap the recap. 500PSI means NOTHING unless every single diver on the boat is using the same cylinders and it's been agreed what the basic minimum volume of remaining gas is acceptable.

I hear what you're saying. I personally have never used anything but an AL80, and since this is in the New Divers Forum, I guess I assumed that was pretty standard. However, that could have been a bad assumption. I honestly don't know what an acceptable PSI would be with that tank configuration.

 

[MXGratefulDiver]

Did any of your gauges indicate more air than actual or were they all biased like mine to read less than actual?

The ones I tested typically showed zero before they actually stopped breathing ... but I did have one that showed 200 psi. I suspect that, by design, they're biased toward showing lower than the actual amount of gas in the cylinder ...

... Bob (Grateful Diver)

 

[syntaxerrorsix]

I hear what you're saying. I personally have never used anything but an AL80, and since this is in the New Divers Forum, I guess I assumed that was pretty standard. However, that could have been a bad assumption. I honestly don't know what an acceptable PSI would be with that tank configuration.

I should have included the minutiae. As you pointed out this is the new diver forum.


NWGratefullDiver gave a more verbose answer


For help with your planning I'd look into rock bottom gas management.

http://www.scubaboard.com/forums/dir/141671-questions-about-rock-bottom-gas-planning-fundies.html

 

[Kenny13]

I'm wondering if people are confused? Or if it is just me (very possible). It seems like there are a lot of responses about knowing the rule. However, Crush, you were asking if they were taught HOW TO execute the dive so they followed the rule, right?

I guess I'm suprised at how many people have said they learned how to plan out their gas from OW. I was told the rule of thirds, but I don't think that's really a good plan, because different dives require different plans...such as the post that sparked this question. I'm just confused if everyone learned a planning method or just guidelines to go by?

I noticed the same thing as I was reading through most of this yesterday afternoon. Seem to be more responses about knowing the rule than about when/where executing the rule was learned.

For me, gas management was something that was covered in OW class, but very briefly with little detail. Although I have yet to actually do any boat diving, I've heard from multiple sources including my OW instructor the rule of getting back to the boat with 500 psi. I'm not one who believes that holding an OW certification means my learning has been completed and that I'm just ready to go out and do any dive whenever/wherever I please. I want to learn more and be a competent diver who is prepared for any situation that may arise, and I am learning that dive planning and gas management are extremely important aspects of diving. Something that should involve more that just being told "arrive at the boat with 500 psi left in your tank" in the early stages of training.

I have yet to do things like learning my SAC so I can be better at dive planning and gas management. 10 logged dives, including my 4 OW checkout dives, I feel like I need to get more comfortable in the water and better at buoyancy control & trim before I worry about things like SAC. Also, all the diving I've been doing have been at locations where we're 50' or shallower and fairly confined to a small area, so your ascent is always going to be very near your entry point (within 50 yards or so). Therefore, we have focused on things like planning our ascent once any diver reaches the agreed upon PSI, any diver can thumb the dive for any reason, and working on skills.

Hadn't put too much thought before this into how do you arrive back at the boat with 500 psi, and that really shows something that is lacking in diver education. Whether you consider it a topic for recreational diving, technical diving, or somewhere in between, how can recreational divers ever be expected to return with that reserve if they aren't taught how in the first place?

 

[The Chairman]

I think that the rule can be traced back to the j-valve. That's what I first learned to Scuba on. Of course, the real problem wasn't people dying in droves, it was more about water getting into your tank and ruining it. In fact, I don't think I really learned about effective gas management until ScubaBoard. There were a number of deficiencies in my certification including safety stops (we only did safety pauses), gas management and trim/buoyancy. I have made a concerted effort to make sure that my students get this and more.

 

[reo]

... did they specify at what depth this was supposed to work out?

... Bob (Grateful Diver)

Bob - Sorry it took so long to reply. This was for OW dives at 60 ft or less.

Ron